The A-Frame

If you don't know what the A-frame is, it is the portion of the frame that suspends the keys. It consists of 4 beams under the bars parallel to the alignment of the string holes in the keys. This part was very tricky to figure out the exact measurements I would use. Ideally, the string holes are drilled through the nodal points of the bars perpendicularly, but they also have to line up when all the bars are in place. So there has to be some compromise on their location and angle. I decided to determine the nodal point again of every 3 bars or so. The nodal points are now in different locations than they were before any tuning was done.

I had this poster board that I decided to use as a template or stencil of sorts. I positioned all the bars on it with the exact space between each bar that I wanted. It was just barely too small so I extended it to fit the last bar. Then I traced the corners of all the bars.

I then positioned string over the nodal points that I just measured. I had to position it as a best fit line through the nodal points because they don't line up perfectly. With the string taut over the nodal points I marked the lines where the string holes will be drilled on the bars as well as the poster board.

Then I made some measurements on the lengths of the beams that needed to be cut. I'll spare the boring details on how those were determined. Then I cut them to length with a miter saw.

I lined up the beams using my template and then screwed them together. For all purposes of joining pieces of wood together for the frame I first set the pieces in place with wood glue and let them set with clamps.

I used a drill bit smaller than the width of the screws to drill "pre-holes" for the screws. This prevents splitting the wood by driving the screws straight into the wood. I also used a countersink bit to allow the screw head to sit at or below the surface of the wood.

This multi-function oscillating tool worked great for smoothing out the surfaces where different beams are joined together.

Here is the complete A-Frame with the tools used to put it together. That tool in the middle is called a T-Bevel. It was used to find the angle that each of the four beams are positioned on the end pieces. This allowed me to cut the four pieces connecting the pairs of beams together at the proper angle.